1. Field of the Invention
The present invention relates to an outboard motor that propels a vessel and a vessel that includes the outboard motor.
2. Description of the Related Art
A conventional outboard motor includes a water pump that is driven by an engine. The water pump supplies water, taken in from a water inlet that opens at an outer surface of the outboard motor, to a water jacket provided in the engine.
Each of outboard motors disclosed in U.S. Pat. No. 7,867,048 and U.S. Pat. No. 8,002,597 include an exhaust pipe provided with a water jacket and a catalyst housed inside the exhaust pipe. As shown in FIG. 9 of each of U.S. Pat. No. 7,867,048 and U.S. Pat. No. 8,002,597, each outboard motor includes a vent hole (extension pipe 731) that discharges air inside the water jacket to the exterior of the water jacket.
When the water pump is driven by the engine, water outside the outboard motor is taken into the interior of the outboard motor from the water inlet, and the cooling water that is taken in rises inside the outboard motor toward the water jacket. The cooling water is thus supplied to the water jacket. In this process, the air inside the water jacket is discharged to the exterior of the water jacket through the vent hole. The water jacket is thus filled quickly with the cooling water. The cooling water supplied to the water jacket flows down inside the outboard motor towards an exhaust opening provided in a propeller.
The water inlet opens at the outer surface of the outboard motor, and the water inlet may thus be clogged by underwater foreign matter, such as seaweed, etc. There are thus cases where the supply of the cooling water to the water jacket is stopped.
With the conventional outboard motor described above, when the supply of cooling water to the water jacket stops, the cooling water inside the water jacket flows down inside the outboard motor towards the exhaust opening provided at the propeller and the air outside the water jacket flows into the water jacket through the vent hole. The cooling water inside the water jacket is thus discharged quickly.
Even if the supply of the cooling water to the water jacket is stopped, as long as the cooling water remains inside the water jacket, a cooling ability of some degree will be maintained. However, with the outboard motor described above, the cooling water remaining inside the water jacket is discharged rapidly and, therefore, the cooling ability of a cooling system that cools a high temperature portion of the engine, etc., is lowered immediately.